Effect of irrigation with treated municipal waste water ( TMWW ) on soil nematode populations was investigated under field conditions over two growing seasons ( 1988 - 1990 ). Four experiments, each involved one crop ( alfalfa, wheat, tomato and spinach ), were conducted at Dirab Agricultural Experimental Station. In each experiment, irrigation with TMWW or fresh water ( FW ) was tested in split-plots randomized within whole plots of no-control versus control of air-born fungi and insects ( pesticides ). Plots of all experiments were sampled for soil nematodes at three times each season, and soil nematode genera were identified , counted and recorded at each sampling time.
Although irrigation with TMWW gave inconsistent results throughout the sampling times of the crops, it showed a general trend of effect similar to the effect of FW. At more than 60% of sampling times, effects of TMWW were not significantly different from those of FW. In the tomato experiment, and during the second year of all crops except wheat, TMWW never increase nematode populations.
Application of insecticides, generally had an adverse effects on nematode populations. Long term of such study is needed.